1. Field of the Invention
The present invention relates to a scanning-line selecting circuit and a display device using the same. In particular, it relates to a liquid crystal display, or a TFT (Thin Film Transistor) active-matrix liquid crystal display.
2. Description of the Related Art
From conventionally, a proposal has been made concerning a method for driving all of scanning lines by reducing output number of scanning-line driving IC down to one-several tenths, and also by using a scanning-line selecting circuit. Here, this proposal has been made in order to allow a decrease in implementation cost and driving IC cost, an enhancement in reliability, and a reduction in area of non-display portion.
Also, in an a-Si (i.e., amorphous-silicon) TFT, there exists a problem of “threshold-value shift” which is characteristic of the a-Si TFT. Namely, if a voltage higher or lower than a first terminal (drain or source) and a second terminal (source or drain) continues to be applied to a gate terminal (this state is referred to as “DC stress”), the threshold value of the a-Si TFT also shifts to a higher or lower value. There has been such a problem called “threshold-shift.” Accordingly, it is necessary to avoid this problem. Also, it has been found that basically the same problem exists not only in the a-Si TFT also but also in an organic TFT.
In order to avoid this problem of the threshold-value shift in the scanning-line selecting circuit, it is required to configure the circuit such that the DC stress will be suppressed down to the smallest possible degree. Its concrete embodiment has been disclosed in, e.g., JP-A-2002-311879 and the like.